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[SOLVED] root on /dev/md127 will not boot after installation
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pgu
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PostPosted: Mon Nov 24, 2014 6:27 pm    Post subject: [SOLVED] root on /dev/md127 will not boot after installation Reply with quote

I just re-installed gentoo on one of my servers. It used to be based upon grub1, and now I'm using grub2. All I observe is

Code:
Loading Linux 3.16.5-gentoo ...

And then nothing more.

I can boot the install CD and mount the filsystem using that kernel without problems. I have also used my previous .config with all the LVM support etc. from my previous kernel build. I have compiled grub2 with the device-mapper use flag. I have also added lvm to the grub preload modules so I observe:

Code:
### BEGIN /etc/grub.d/00_header ###
insmod lvm

in my /boot/grub/grub.cfg

One difference is that my RAID was shown as /dev/md0 previously, and now it's /dev/md127. So when I run grub2-mkconfig the menuentry will contain:

Code:
        echo    'Loading Linux 3.16.5-gentoo ...'
        linux   /vmlinuz-3.16.5-gentoo root=/dev/md127 ro 


How can I debug this? Is it a grub2 problem, or is it a problem with my kernel?


Last edited by pgu on Tue Nov 25, 2014 3:18 pm; edited 1 time in total
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pgu
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PostPosted: Mon Nov 24, 2014 7:07 pm    Post subject: Reply with quote

Also added domdadm so my /etc/default/grub now contains:


Code:
GRUB_PRELOAD_MODULES=lvm
GRUB_CMDLINE_LINUX_DEFAULT="domdadm"


Still the same.
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pgu
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PostPosted: Mon Nov 24, 2014 7:11 pm    Post subject: Reply with quote

Is it possible to specify the UUID rather than the device when I have the domdadm kernel parameter?
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pgu
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PostPosted: Tue Nov 25, 2014 5:48 am    Post subject: Reply with quote

I would assume this is more of a problem of booting the kernel file rather than mounting the md filesystem as I don't get any output from the kernel, only the grub message.
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pgu
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PostPosted: Tue Nov 25, 2014 7:14 am    Post subject: Reply with quote

http://wiki.gentoo.org/wiki/GRUB2#Configuration says:
Quote:
grub2-mkconfig does not work properly with mdraid. Unless you manually fix up the config afterwards you will be left with a non-bootable system!


What are these manual fixes? I don't have my boot partition on mdraid, only my root. But what are the manual fixes?
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nativemad
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PostPosted: Tue Nov 25, 2014 12:11 pm    Post subject: Reply with quote

Hi,

it's strange that it doesn't show more... What happens if you take a kernelfile that isn't existing?? - Press E to edit the parameters within the grub menu :wink:
Are you sure you need lvm and devicemapper at all, when you use the md device directly as root??
What kind of raid do you have?
I never had luck without an initrd and root on mdraid5/6.....
...If the Kernel doesn't assemble the raid on it's own, then you'll need to help out with mdadm, which is normally within the initrd...
Code:
genkernel --mdadm --no-clean --menuconfig all

That should do it!
And do not forget to add "domdadm" as kernel parameter!! :!:

HTH, cheers
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pgu
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PostPosted: Tue Nov 25, 2014 3:18 pm    Post subject: Reply with quote

The initrd solved the problem. Thanks! For some strange reason I though I did not need it for grub2.

I probably don't need the device-mapper and lvm at all.
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